The concept of blood separation is known and several methods and materials are available to accomplish such separation. For instance, wet-laid technology utilizes essentially single layers with a blend of natural and man made fibers. Exemplary are single layer blood separation media utilizing composites such as glass microfibers, cellulose fibers, and synthetic textile fibers. Membrane technology can utilize a graduated pore structure from upstream to downstream for effective RBC separation. Blood separation media made of non-woven webs of fibrillated and non-fibrillated synthetic staple fibers are also known.
Known techniques have drawbacks including undesirable hemolysis, non-uniform thickness of media, low yields of the fluid fraction of plasma, slow absorption of blood, and unsuitability across a range of hematocrits.